1. Field of the Invention
This application concerns a cooling system for a vehicle""s internal combustion engine including a radiator having a closure assembly and, more specifically, to a specific cap-type closure assembly including a normally open fluid venting valve for regulating flow of fluid out from the radiator. The fluid venting valve closes to produce pressurization of the cooling system in response either to elevated temperature of the cooling system or to outward fluid flow from the radiator.
2. Description of the Related Art
Typically, a cap-type closure assembly is used to close a filler opening of a radiator. A desirable type of closure assembly has a normally opened fluid venting valve mechanism to permit either gaseous or a small quantity of liquid fluid to exit the radiator and pass to a fluid venting overflow circuit. As the engine temperature increases, such as during a warm-up mode of operation, the fluid in the cooling system and any air in the radiator is expanded. The thermal expansion of the liquid in the cooling system urges any air past the closure cap""s fluid venting valve mechanism. The fluid venting valve mechanism closes in response to a particular flow rate of air passing the venting valve which thereafter seals or closes the radiator""s filler opening allowing for pressurization of the vehicle cooling system.
It can thus be understood that after the vehicle engine reaches a desired operating temperature, the cooling system including the radiator is pressured. Then when the engine is shut-down or deactivated, the fluid temperature in the radiator will decrease in temperature and pressure. Eventually, the fluid venting valve mechanism opens to allow fluid to reenter the radiator from an overflow storage system. Accordingly, this type of closure assembly with a fluid venting valve mechanism is designed to reopen as the pressure in the radiator decreases, thus depressurizing the radiator. Normally when the engine is again restarted, the above described engine warm-up and fluid expansion process is repeated.
The present application concerns a normally opened type closure assembly as previously described but with an additional thermally reactive construction for closing the fluid venting valve mechanism and the radiator filler opening in response to a particular range of elevated temperatures of the cooling system including its environment. Thus, deactivation of an engine at operating temperature even when accompanied by a decrease in radiator pressurization will not result in opening of the closure assembly""s fluid venting valve mechanism. The venting valve will remain closed until the cooling system and radiator environment cool sufficiently to permit the thermally reactive construction to open the valve. Thus, pressurization of the cooling system is maintained for a significant period of time sufficient to avoid the repressurization cycle when the warmed engine is again restarted. The elimination of the necessity to repressurize the radiator decreases response time necessary for the cooling system to attain maximum cooling capacity.
Accordingly, it can be appreciated that there is a need for a radiator closure assembly that seals or closes the radiator not only in response to either an air flow or a coolant flow through the closure assembly, but also in response to the temperature environment of the cooling system. Thus, the flow of fluid out from the radiator normally controls the sealing of the radiator during an engine warm-up mode of operation. But a continuation of radiator pressurization is maintained for a sufficient period of time after engine shutdown so that upon start-up again repressurization of the cooling system is eliminated.
The closure cap assembly defines a fluid vent passageway which is communicated with a fluid venting mechanism or movable valve with an opened operative position and a closed operative position. As with a typical previous cap assembly, the fluid venting mechanism operates in response to a predetermined rate of fluid flow passing by the valve. Further, the fluid venting mechanism includes a thermally responsive spring which urges the venting valve mechanism from an opened operative position to a closed operative position in response to an increased temperature of environment of the engine cooling system. This temperature responsive feature maintains pressurization of the cooling system for a sufficient period of time after engine shutdown so that an already warmed-up engine can be restarted and immediately operated with a pressurized cooling system.
Further, this temperature responsive feature and venting valve mechanism closes the fluid venting system upon sensing an elevated system temperature even if the flow responsive portion of the fluid venting mechanism does not close the venting system.
Accordingly, one advantage of the thermally reactive radiator closure cap assembly is that it will initially close-off the venting valve mechanism and maintain pressurization of the cooling system in response to the temperature of the engine and cooling system.
Another advantage of the thermally reactive radiator closure cap assembly is a reduction of thermal cycle related stresses on the system since the frequency of pressurization/depressurization of the radiator is lessened so that the cooling system remains pressurized during a significantly greater portion of effective vehicle operation.
Finally, these advantages are achieved in a simple but effective thermally reactive radiator closure cap assembly that is cost-effective to manufacture relative to more complex solutions thus far proposed.